1) Glock 23 and 32 are EXACTLY the same (as are the 31/22 and 27/33) except for the number on the side of the slide. Even the mags are exactly the same except for 357 instead of 40.

2) You don't even need a "conversion" barrel. There is nothing to convert. You can use an OEM Glock barrel of the other caliber to switch from 40 to 357. Thus, but a GLOCK barrel for a G32 and you can put it right into your G23, using the exact same magazines, extractors, ejectors, recoil springs, everything. Easiest "conversion" to make.

Not to test anyone's patience, but please bear with me as I am very new to Glock. I don't want to convert a 23 to a 357sig, I want to convert to 9mm. Does what you said still apply? All I would need is a barrel and a magazine?

Not to test anyone's patience, but please bear with me as I am very new to Glock. I don't want to convert a 23 to a 357sig, I want to convert to 9mm. Does what you said still apply? All I would need is a barrel and a magazine?

You would need an aftermarket conversion barrel but yes. I've had pretty good luck with 40 mags with 9mm but it's better to just get one

Not to test anyone's patience, but please bear with me as I am very new to Glock. I don't want to convert a 23 to a 357sig, I want to convert to 9mm. Does what you said still apply? All I would need is a barrel and a magazine?

The .40 and the .357 Sig have the same case head dimensions and OAL so they are very easy to convert using just a barrel. Magazines are EXACTLY the same.

Converting from .40 (or .357 Sig) to 9mm is a little more problematic. The case head is different, but Glock (and S&W) use an extractor configuration that works with both (99% of the time). A barrel swap is the most expensive part. Some have good luck with the .40 mags feeding the smaller 9mm round. Some have some hiccups. Best to use 9mm specific mags.
With my 10mm to 9mm conversion I have found the 10mm mags work pretty well. I just cannot load the mag to full capacity. I down load by 2 and they work fine. There are no large frame mags for the 9mm.

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Some people also switch out the extractor to make sure it pulls out the empty 9mm shell cases. If you do this, which isn't necessary, but may increase dependability, you switch the extractor (to a Lone Wolf LCI 9mm model, which has a marking making it easier to identify $7) and a spring-loaded bearing (Glock OEM is fine, also from Lone Wolf $3). You can keep the spring in there and the plunger, since those are the same for 9mm/40/357.

These changes take a few minutes to convert and are not necessary. But if you plan to keep it a 9mm for longer periods of time and not just a range session, you may want to do this for only $10 and 10 minutes.

The .40 and the .357 Sig have the same case head dimensions and OAL so they are very easy to convert using just a barrel. Magazines are EXACTLY the same.

Converting from .40 (or .357 Sig) to 9mm is a little more problematic. The case head is different, but Glock (and S&W) use an extractor configuration that works with both (99% of the time). A barrel swap is the most expensive part. Some have good luck with the .40 mags feeding the smaller 9mm round. Some have some hiccups. Best to use 9mm specific mags.
With my 10mm to 9mm conversion I have found the 10mm mags work pretty well. I just cannot load the mag to full capacity. I down load by 2 and they work fine. There are no large frame mags for the 9mm.

Exactly.

Let's say for example, you have a G23 that you intend to convert...

357sig- You can spend $120 on a Lone Wolf 357sig (G32) barrel and you're done.

9mm- You should not simply buy a G19 barrel. Rather, you want a G23 40-9 'conversion' barrel. Basically, things don't quite line up laterally without it. The G19 and 40-9 barrels cost the same, so you may as well take care to get it right. For the most part, 40sw/357sig mags will feed 9mm flawlessly. But adding some G19 mags would be ideal.